Hillshire Brands Co. agreed to buy Pinnacle Foods Inc. for $4.3 billion in a bet that mixing hot dogs and frozen cakes with pickles, syrup and salad dressing will add up to a more appetizing business.

The deal, announced Monday, would create a company with about $6.6 billion in annual revenue and a broad array of brands including Hillshire's namesake lunch meats, Jimmy Dean sausages, Ball Park hot dogs, and Sara Lee frozen desserts...